Listen closely. Inside the cabin they discover an interesting clue - another copy of Not Without Peril, the book Maura left behind in her car. One could argue that it is a very popular book in the area around the White Mountains. But as someone whose business is books, I can tell you a book like that did not have a very large print run. It's a very specific local-interest sort of book. And it would not be available in most bookstores, even out there. It's more likely it was available in local hiking-supply stores or White Mountains visitors' centers. To me, that book is evidence of a connection to Maura Murray. As in she ran with the crowd that frequented the cabin back then.
**UPDATE** I stand corrected. Not Without Peril has sold over 70,000 copies. Damn. That's impressive.